I think that it kinda depends on what you want to do with the wood. Firewood can be snapped, broken with a big rock (or foot), left long and one end shoved in the fire as needed, etc. "Construction," on the other hand, could require a more precise division of the wood. And even if you have an axe, a GOOD saw usually requires less effort than an axe, and is much quieter to boot (which might be a concern in some situations)...